this extension is about drawing a dynamic graph, which scrolls to the left.
in this post we have a code to draw a dynamic graph:
Redirecting to Google Groups
In this topic I simplified that code and made several examples:
Dynamic graph. Sinusoidal wave. Shift left graph
Now this extension performs the same effect.
You can download the extension from:
App Inventor. Extensión. Dibujar un gráfico dinámico.